package com.gupao.vip.nio;

import cn.hutool.core.util.StrUtil;
import org.apache.commons.io.IOUtils;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Iterator;
import java.util.Objects;
import java.util.Set;

public class MultiplexerTimeServer implements Runnable {
    private Selector selector;

    private ServerSocketChannel servChannel;

    private volatile boolean stop;

    public MultiplexerTimeServer(int port){
        try{
            selector = Selector.open();
            servChannel = ServerSocketChannel.open();
            servChannel.configureBlocking(false);
            servChannel.socket().bind(new InetSocketAddress(port), 1024);
            servChannel.register(selector, SelectionKey.OP_ACCEPT);
            System.out.println("The time server is start in port ：" + port);
        }catch(IOException e){
            System.err.println("init MultiplexerTimeServer fail! " + e.getMessage());
            System.exit(1);
        }
    }

    public void stop(){
        this.stop = true;
    }

    @Override
    public void run() {
        while(!stop){
            try{
                selector.select(1000);
                Set<SelectionKey> selectionKeys = selector.selectedKeys();
                Iterator<SelectionKey> it = selectionKeys.iterator();
                SelectionKey key = null;
                while(it.hasNext()){
                    key = it.next();
                    it.remove();
                    try{
                        handleInput(key);
                    }catch(Exception e){
                        if(Objects.nonNull(key)){
                            key.cancel();
                            if(Objects.nonNull(key.channel())){
                                key.channel().close();
                            }
                        }
                    }
                }
            }catch(Throwable t){
                System.out.println(t.getMessage());
            }
        }

        //多路复用器关闭后，所有注册在上面的Channel和Pipe等资源都会被自动去注册并关闭，所以不需要重复释放资源
        IOUtils.closeQuietly(selector);
    }

    private void handleInput(SelectionKey key) throws IOException{
        if(key.isValid()){
            //处理新接入的请求消息
            if(key.isAcceptable()){
                ServerSocketChannel ssc = (ServerSocketChannel)key.channel();
                SocketChannel sc = ssc.accept();
                sc.configureBlocking(false);
                sc.register(selector, SelectionKey.OP_READ);
            }

            if(key.isReadable()){
                SocketChannel sc = (SocketChannel)key.channel();
                ByteBuffer readBuffer = ByteBuffer.allocate(1024);
                int readBytes = sc.read(readBuffer);
                if(readBytes > 0){
                    readBuffer.flip();
                    byte[] bytes = new byte[readBuffer.remaining()];
                    readBuffer.get(bytes);
                    String body = new String(bytes, "UTF-8");
                    System.out.println("The time server receive order : " + body);
                    String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? LocalDateTime.now().format(DateTimeFormatter.ISO_DATE_TIME) : "BAD ORDER";
                    doWrite(sc, currentTime);
                }else if(readBytes < 0){
                    //对端链路关闭
                    key.cancel();
                    sc.close();
                }
            }
        }
    }

    private void doWrite(SocketChannel channel, String response) throws IOException{
        if(StrUtil.isNotEmpty(response)){
            byte[] bytes = response.getBytes();
            ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
            writeBuffer.put(bytes);
            writeBuffer.flip();
            channel.write(writeBuffer);
        }
    }
}
